8 
THE ART OF REARING 
The colour of caterpillars that have just cast 
their skin is pale, which serves to distinguish them 
from others. The new skin is much wrinkled, 
while the old one was dry and puckered, at the 
beginning. The fasting, exhaustion, inactivity, 
and disorder that accompany the casting of the 
skin are what are commonly called the sleep of the 
silk-worms. The caterpillar is much exhausted 
by this action, and the parts of his body which 
before were hard are now more flexible ; thev 
harden by the contact alone of the air. After the 
last casting of skin, each sort of caterpillar spins 
the silk, and prepares with it the cocoon or retreat, 
in which the changes into a chrysalis, and after- 
wards into a butterfly, or perfect animal, produc- 
ing eggs that generate caterpillars, are to take 
place. 
With most caterpillars the exterior castings of 
the skin, as well as those two which take place 
within the cocoon, require fifteen days (§ 4, 5,) 
In some species this process occupies one or two 
months, in others three months, and in some again 
it requires one, three, or even four years. 
3. Of the Manner in which Caterpillars live, nou- 
rish, and preserve themselves. 
Without speaking here of some kinds of cater- 
pillars that live by devouring one another, all 
the others, which are very numerous, exist on vege- 
